This invention relates to a plant fiber composite material, more particularly to an environmentally benign plant fiber composite material. This invention also relates to the products of the composite material and a processing method for the plant fiber composite material and extruded or molded products using the plant fiber composite material.
To eliminate xe2x80x9cwhite pollutionxe2x80x9d, substitutes for plastics and foamed plastics have been searched for all over the world, particularly focusing on disposable tableware and products made from plant fiber. At present, there are more than 100 disclosed patent technologies of disposable tableware and products utilizing plant fiber as major raw material in the world such as in the United States, Japan, Germany, Switzerland, Thailand etc, in which more than 60 patent technologies were disclosed in China. However, only a few have commenced commercial production, and the type of products have not been put into market in a large scale for substitution of plastics and foamed plastics. The first reason is the higher cost of the product using plant fiber for raw material, because the plant fiber will result in heavier weight of products, take fast food lunch box for an example, each foamed plastic fast food lunch box only weighs 5 g, each paper lunch box weighs 25 g, and each plant fiber lunch box weighs 50 g, and the cost is greatly decided by the material weight. The second reason is the dark color being disliked or unacceptable by the consumers and the third reason is the poor quality that will result in higher damage rate in transportation or utilization.
However, viewing from current disclosed patent technologies, although the material formulations of various disposable tableware and products and/or appliances are not identical, three processing methods (xe2x80x9cslurrying mouldxe2x80x9d, xe2x80x9cwet cold pressingxe2x80x9d and xe2x80x9cDry hot pressingxe2x80x9d technologies) have been adopted predominantly. However, all of the three processing methods are intermittent processes, and are unable to form a continuous streamlined production process.
One object of the invention is to provide a plant fiber composite material with a biodegradation function, that is an ecological environment protection material.
Another object of the invention is to provide an application of the plant fiber composite material in manufacturing tableware, products, and/or appliances.
A further object of the invention is to provide a processing method of the plant fiber composite material in tableware, products, and/or appliance fabrication, that is a continuous streamlined production process.
The plant fiber composite material of the invention comprises the following components in relative weight parts (by weight in parts):
plant fiber 60-80 parts
polycarbonate resin 5-30 parts
food coloring agent 0-5 parts
wherein the molecular weight of said polycarbonate resin is 8000-35000.
The plant fiber of the invention is obtained from a crop waste, including, but not limited to rice husk, ricegrass, wheat bran, wheat straw, beanstalk, cotton stalk, forage grass, peanut shell, cornstalk, sorghum stalk, bagasse, coconut shell, residue of sugarcane, residue of orange juice, sawed timber bits, bamboo ash and the mixtures thereof. The amount of said plant fiber is preferably in the range of 70 to 80 parts by weight.
Preferably, the polycarbonate resin of the invention is polymerized 2,2xe2x80x2 (4 hydroxylphenyl) propane carbonate monomer.
Preferably, the molecular weight of the polycarbonate resin is 10000-15000, and the amount of the polycarbonate resin is in the range of 15 to 20 parts by weight.
The food coloring agent of the invention is selected from the group consisting of titanium white, zinc oxide, iron oxide red, pigment yellow 147, pigment blue 15, and combinations thereof. Preferably, the food coloring agent is titanium white. Preferably, the amount of the food coloring agent is in the range of 4 to 5 parts by weight.
The plant fiber composite material of the invention can further comprises 5-15 weight parts of 4,4xe2x80x2-biphenyl methane diisocyanate (MDI), and preferably 3-5 parts by weight.
The processing method of continuous streamlined production process for production of tableware, products, and/or appliances using plant fiber composite material of the invention comprises the following steps:
1. Place the pulverized plant fiber into the hopper of plant fiber expander, add water corresponding to 10-30% of the plant fiber by weight into the expanding chamber, turn on the expander, and then the plant fiber is expanded and prepared into a powder;
2. Place above expanded plant fiber powder, polycarbonate resin, food coloring agent and/or MDI proportionally into a vertical stirring mixer, thoroughly mix them for 10 min to form a mixture, then add the mixture into a granulator, and the granules of the plant fiber composite material is prepared under 120-200xc2x0 C.
3. Place above granules into a bunter of the hopper of a twin-screw extruder, control the extrusion processing technologies parameters of the twin-screw extruder as follows to extrude the granules into a sheet continuously:
cylinder temperature 220-250xc2x0 C.
connector temperature 230-280xc2x0 C.
die temperature 250-300xc2x0 C.
extrusion pressure 15-30 Mpa
extrusion speed 1-10 m/min
4. Continuously convey above extruded sheet to a puncher connected with the twin-screw extruder, and then punch and mold the sheet with heated moulds at 150-250xc2x0 C., 2-50 kg/cm2, to obtain the final products.
In the invention, the size of said expanded plant fiber powder is 10-120 mesh, preferably 20-40 mesh, water content of the expanded plant fiber powder is 20-50%, preferably 30%.
Preferably in this invention, the processing technological parameters of extruding the granules of the plant fiber composite material in the twin-screw extruder are as follows:
cylinder temperature 220xc2x0 C.
connector temperature 230xc2x0 C.
die temperature 250xc2x0 C.
extrusion pressure 25 Mpa.
Said extruded sheet is a plate sheet or an open heterotypic sheet.